20 March: evolution and devolution, big cats and other things.

Evolution
Jerry Coyne has an interesting post on mimicry in nature: this happens when one animal evolves to resemble something else; for example, sometimes an animal can evolve to look like something that preys on its natural enemies. However, read the post all the way down; there is a case in which the females evolved more mimicry than the males: though more mimicry might help the males live longer, it might have cost them potential mates if the females retained preferences for the “lesser evolved” males.

A new study out of the University of Tulsa in Oklahoma seems to suggest that the cliff swallows there are adapting to their modified environments in an interesting way. Researchers found their wings may be getting shorter to help them take get out of the way of traffic.

“We found that by picking up dead birds killed by vehicles over the last 30 years, the wing lengths on these birds has changed, and we’re finding many fewer dead birds now than we were finding 30 years ago,” said Professor Charles Brown of University of Tulsa in Oklahoma. “So it looks like something is going on in the population enabling these birds to better avoid being hit by cars.”

According to data collected in the study, the swallows’ wing span decreased about 10 percent. Though that is not a large number, Brown says it’s significant because it’s happening in birds.

“It’s actually quite a bit as bird morphology goes,” said Brown. “Bird morphology is fairly static, it doesn’t really change much in response to selection, and this is actually a very dramatic change in a morphological trait.”

Though scientific evidence points to how natural selection allowing swallows to avoid being killed by vehicles, there are many other environmental factors that can contribute to such a evolution. For instance, Brown says that a change in the availability of insects, the bird’s natural prey, and changes to their habitat are factors to consider. Also, natural selection fluctuates over time, so adaptations we’re seeing now could cease to exist in the long term.

We shall see. Interesting, no?

I don’t get this behavior
I am not a Big Cat person (at all) but this is an awesome short video. It shows a cheeta paying a visit to some tourists in a tourist truck. It doesn’t really threaten the people in the truck, but it gets up close and personal; it “almost” behaves like a pet….a standoffish pet.

Here is a very simple, yet little-known result that proved useful to me recently. I’m surprised it is not better known, since it seems to be a natural question.
Suppose you have a directed graph G = (V,E) with n vertices that is strongly connected (so there is a directed path from every vertex to every other vertex). Consider the length of the shortest closed walk W that visits every vertex. In the worst case, how long can W be?

Here, as usual, by a “closed walk” we mean that we start at some vertex and return to it, and we are allowed to repeat vertices and edges. We measure the length of W by the number of edges, and write it as |W|. Such a walk is sometimes called a “Hamiltonian walk” in the literature.

The answer is floor((n+1)2/4). This simple result was apparently first proved by Yahya Ould Hamidoune, in Proposition 2.1 of his paper published in Discrete Mathematics 26 (1979), 227-234. Hamidoune just recently passed away; he was apparently one Mauritania’s most famous mathematicians, and proved many deeper results than the little proposition above. But his graph inequality might prove useful to others, so I reproduce his proof here.

Surf to Shallit’s blog to see the proof; it is one that, even if you aren’t a specialist, you can get something out of (with some intellectual effort).

Some readers have asked me to reply to this Steve Keen piece claiming that I don’t understand the IS-LM model. Sigh. I really don’t want to spend time fighting against people with whom I don’t really have a current policy disagreement — and this is so silly, besides. But to satisfy those who are for some reason nervous, here’s a brief explanation of why somebody doesn’t understand IS-LM.[…]

He then says, aha! The IS market is out of equilibrium when we’re in a liquidity trap, but Krugman writes as if it were in equilibrium! Gotcha!

Um, it pays to read the labels. Those savings and investment curves are what the supply and demand for funds would be if the economy were at full employment. They’re not the curves that actually apply when the economy is operating below full employment. In the IS-LM model, the quantity of funds supplied is always equal to the quantity of funds demanded — because the level of output adjusts. This is true both when the zero lower bound applies and when it doesn’t. […]

So what Keen thinks is a big logical fallacy on my part is just a failure of reading comprehension on his part.

Look, IS-LM could be all wrong; but I am accurately reflecting the way that model works. And while I am not infallible, I have done a lot of economic modeling in my time; if you think that I’ve made an elementary logical error, you might want to check your reasoning very carefully before going with it.

Seriously folks. These smart, famous people are sometimes wrong about conjectures or sometimes make mistakes. But they almost NEVER make “elementary mistakes” such as these. If you think that your “common sense” has found an elementary flaw in their work, YOU are almost certainly wrong.

All of which raises an interesting question: why don’t people like Hinderaker who have been wrong about everything for years and years — demonstrably wrong, in ways that would have lost anyone who believed them a lot of money — ever reconsider? Shouldn’t the thought at least enter their minds that maybe economic analysis is not their strong point? Shouldn’t they at least entertain the notion that they are talking to the wrong “experts”?

So why doesn’t this happen? Part of it, surely, is the Dunning-Kruger effect: the truly incompetent are too incompetent to realize that they’re incompetent. Part of it, also, is the Madoff “affinity fraud” effect: people trust someone they perceive as part of their tribe — in this case the tribe of liberal-haters — and are blind to evidence that they are being taken for a ride.

The surprise, I’d say, is just how strong the Dunning-Kruger-Madoff effect has proved in the face of economic crisis. Year after year in which the predictions of their crowd have gone totally astray haven’t shaken their faith at all. They still believe that reading the WSJ editorial page and watching Fox are the way to know what’s going to happen to the economy, and nothing will change their minds.

Here is what I think that Krugman misses (remember, this is NOT economic policy but a conjecture as to why Fox and company stays in business despite getting just about everything wrong):

The Wall Street Journal and Fox are more about entertainment than anything else. People(*) often see “truth” as “what makes sense to me” and “what confirms what I already think”. These media outlets cater to that crowd. Accuracy is of no importance; it is about keeping the reader entertained.

(*): I used to think of this as a characteristic of conservatives, but have found that it really isn’t “just” conservatives. I am prone to making this mistake too and therefore have to be vigilant.

About Blueollie

To keep track of my sports activities. I rarely train for anything anymore; mostly I just do workouts of the following types: running, walking, weight lifting and swimming. My best ultra accomplishment was walking 101 miles in 24 hours in 2004. These days, I walk a marathon every once in a while (5:50 to 7 hours) There was a time when I could run a sub 40 minute 10K (did that once), but that was another lifetime ago; these a days 2427-2825 25:50-27:45 minutes for a 5K would be more like it. I also have an off and on interest in yoga and in weight training. My lifetime PB in the bench is 310; currently I do sets of 4-5 with 190.

To discuss the football, basketball or baseball game I’ve been to. Since 2011, I started to attend live football games regularly (University of Illinois, sometimes Illinois State, sometimes either the Colts or Bears of the NFL…don’t get me started on the Rams) ; I’ve attended Bradley Basketball games (men and women) for some time. In the past 3 years, I started to watch live baseball again (mostly the Peoria Chiefs and Bradley University).

From time to time, I post what I am thinking about mathematically

I often post links to science articles, especially articles about cosmology and evolution.

I am very sympathetic to the “new atheist” movement, though some might consider me to be an agnostic. I reject any notion of a deity that interferes with physical events, but remain agnostic to the idea that there might be something “grand and wonderful” (Dawkins’ phrase) outside of our current spacetime continuum.

I am a liberal Democrat who thinks that the current social atmosphere is tilted way too far toward the interests of big business, and I reject the idea that a “free market” cures all ills, though pure socialism doesn’t work either. I am also a believer in the freedom of speech, including speech that I might not like. Also, I’ve been involved (to a moderate degree) with political campaigns, ranging from City Council races up to Presidential races.

I like to post photos of trips and vacations.

I like women in spandex. 🙂

The 2016 election: I voted for Hillary Clinton and was dismayed that she lost the Electoral College, though I take a bit of comfort that a plurality of voters preferred her (by just over 2 percentage points!)

I see Donald Trump as an unqualified amateur who lacks the humility and deportment to be an effective president; I sure hope the time proves me wrong. I’ve been wrong before (e. g. my election prediction) and will be wrong again. I hope this is one of those times.